Digital cameras have been widely used in a variety of applications. With the advent of some new applications, such as cellular phones, vehicles and security and medical appliances, digital cameras are miniaturized to be adapted for easy mounting. Accordingly, camera module, a component of digital cameras, is required to have low manufacturing cost and small horizontal and vertical occupation areas for its suitability for many applications. Such camera modules may be manufactured on a single wafer by using wafer-level technology and packaging technology, and then the wafer-level camera modules are singulated into individual camera modules.
FIG. 1 shows a conventional metal housing of a camera module. The housing includes a quadrilateral top plate 102 and four side plates 108. The top plate 102 is adapted to protect a camera module 120. Referring to FIG. 2, the camera module further includes a sensor 122 and a lens 124 that is disposed on the sensor 122. The top plate 102 includes a light through hole 104 which allows incident light to pass through and reach the lens 124 of the camera module 120. The light through hole 104 is covered with a film (not shown) for protecting the camera module from possible damages in subsequent processes. The side plates 108 are fixed to four sides of the quadrilateral top plate 102, respectively, and each of them includes an opening 110 and a supporting leg 112. Out of the four side plates 108, oppositely disposed two have their openings that are larger than those of the other two which are also disposed opposite to each other. The metal housing is attached to the camera module 120 by ultraviolet (UV) adhesive dispensed through the openings 110. Moreover, as shown in FIG. 3, the supporting legs 112 of the metal housing are soldered to solder balls 114 (not shown) attached to a bonding pad of a printed circuit board (PCB).
The above described design suffers from various deficiencies. One deficiency is that the metal housing is separated from the camera module by a great spacing in all three dimensions, and especially in the Z direction (along the height of the metal housing). The great spacings are highly prone to lead to positional deviations between the metal housing and the camera module during the packaging process and therefore further to a poor packaging precision between the solder balls of the PCB and the metal housing with the camera module packaged therein. This will cause cold solder joint between the metal housing and a printed circuit board assembly (PCBA) during the surface mount technology (SMT) process. Moreover, the cold solder joint will harm the reliability of the resulting housing after the assembled metal housing and camera module were soldered to the PCB.
Another deficiency is that the great spacing between the metal housing and the camera module in the Z direction, coupled with the existence of tolerances of their heights in the same direction, may cause the occurrence of inclination between the metal housing and the camera module during the process of assembling them together when the metal housing is not sufficiently fixed in the Z direction by the UV adhesive dispensed through the openings 110.
In addition, still another deficiency is that openings of the two side plates 108 with larger openings (e.g., the two side plates 108 opposite to each other in the Y direction, i.e., along the length of the metal housing) expose signal pick-up electrodes disposed on side faces of the sensor of the camera module, leaving the camera module unprotected in the Y direction throughout the subsequent assembly processes. Considering that bumps cannot yet be totally prevented in the current manufacturing technology, once a bump occurs, the exposed signal pick-up electrodes disposed on the sensor which are not protected by the metal housing in the Y direction are very likely to be cracked, which will lead to product failure and defects. Thus, as the sensor 122 of the conventional camera module 120 with the metal housing is unprotected in the Y direction, it is vulnerable to impact in this direction.
Moreover, still yet another deficiency is that the great spacings between the metal housing and the camera module in the X and Y directions (i.e., along the width and the length of the metal housing, respectively) may cause deviations in alignment to a center of the light through hole 104 during the process of assembling the metal housing and the camera module together. This may lead to inaccurate alignment between the light through hole 104 and the lens 124.
Furthermore, as there is a great color difference between the metal housing and the lens 124, the metal housing is generally painted to make the outer surface color of the quadrilateral top plate 102 same with that of the lens 124. However, outer surface of the quadrilateral top plate 102 may be scratched by a clip which is used in the assembly process to pick up the metal housing and place it to cover the camera module. Moreover, removal of the film covering the light through hole 104 after the completion of all subsequent processes may also lead to local loss (falling off) of paint applied on surface of the metal housing and hence harm its appearance.
Still yet another deficiency is that although UV adhesive can be conveniently dispensed through any of the four side plate openings 108, in order to cure the dispensed UV adhesive, this design generally requires moving a point light source individually close to each opening. This practice is inefficient.